HYDROPHILIC COMPOSITE

Abstract

Hydrophilic composite structures are made by impregnating a 3DL structure with a polyurethane foam formulation and curing the formulation to produce a foam that occupies the spaces in the 3DL structure. The composite structures have an unusually good capacity for retaining water even when under compressive forces. They also exhibit at most moderate swelling when saturated with water. The foam is useful as a layer of a water containment system such as a green roof or blue roof system.

Claims

1. A composite structure comprising: (a) a three-dimensional random loop (3DL) structure comprising a plurality of random loops of a thermoplastic polymer arranged and bonded together in a three-dimensional orientation and defining spaces within the 3DL structure; and (b) a hydrophilic polyurethane foam that occupies substantially all of the spaces in the 3DL structure.

2. The composite structure of claim 1 wherein the 3DL structure has an apparent bulk density of 0.005 g/cm.sup.3 to 0.2 g/cm.sup.3.

3. The composite structure of claim 2 wherein the hydrophilic polyurethane foam is a reaction product of a reaction mixture comprising i) at least one polyisocyanate, ii) water, iii) a foam-stabilizing surfactant and iv) optionally one or more at least difunctional isocyanate-reactive materials different from water, wherein the reaction mixture contains 30 to 75% by weight oxyethylene units based on the combined weight of components i) and iv).

4. The composite structure of claim 2 wherein the thermoplastic polymer is an olefin polymer or copolymer.

5. A method of making a composite structure comprising the steps of: (I) forming a reaction mixture comprising i) at least one polyisocyanate, ii) water, iii) a foam-stabilizing surfactant and iv) optionally one or more at least difunctional isocyanate-reactive materials different from water, wherein the reaction mixture contains 30 to 75% by weight oxyethylene units based on the combined weight of components i) and iv), (II) impregnating a 3DL structure with the reaction mixture, the 3DL structure comprising a plurality of random loops of a thermoplastic polymer arranged and bonded together in a three-dimensional orientation and defining spaces within the 3DL structure to impregnate the 3DL structure with the reaction mixture; and (III) curing the reaction mixture such that the reaction mixture expands and cures to form a hydrophilic polyurethane foam that occupies substantially all of the spaces in the 3DL structure.

6. A single- or multilayer mat, wherein the mat includes at least one layer of a composite of claim 2.

7. A water containment system comprising a composite claim 2.

8. A water containment system comprising at least one water barrier layer, at least one layer of the composite structure of claim 2 directly or indirectly on top of at least a portion of the water barrier layer, and at least one top surface layer positioned directly or indirectly on top of at least a portion of the hydrophilic foam layer, the water containment system comprising drainage means for draining water falling upon the top surface layer to the hydrophilic foam layer.

9. The water containment system of claim 8 wherein the top surface layer includes soil and vegetation layers and the drainage means include pores in the soil layer in fluid communication with the composite structure.

10. The water containment system of claim 9 wherein the hydrophilic polyurethane foam layer has one or more channels on a bottom surface, which channels form pathways through which water can flow and be removed from the water containment system.

11. The water containment system of claim 9 further comprising a support structure directly or indirectly below the water barrier layer.

12. The water containment system of claim 11 wherein the support structure is a roof structure.

13. A water containment system comprising a support structure, at least one water barrier layer directly or indirectly above at least a portion of the support structure, at least one layer of the composite structure of claim 2, directly or indirectly on top of at least a portion of the water barrier layer, a separation fabric directly or indirectly on top of at least a portion of the hydrophilic polyurethane foam layer and at least one top surface layer positioned directly or indirectly on top of at least a portion of the separation fabric, the water containment system comprising drainage means for draining water falling upon the top surface layer to the hydrophilic foam layer.

14. The water containment system of claim 13 wherein the hydrophilic polyurethane foam layer has one or more channels on a bottom surface, which channels form pathways through which water can flow and be removed from the water containment system.

Description

[0069] The FIGURE illustrates an embodiment of a water containment system of the invention. Water containment system 9 includes, generally, support structure 1; optional insulation/root barrier structure 2; water barrier layer 3; drainage layer 4; filter or separation fabric 5; growth medium layer 6 and vegetation layer 7. The composite structure of the invention forms all or a portion of drainage layer 4.

[0070] Support structure 1 is a load-bearing layer that supports the overlying structures. It can be of concrete, reinforced concrete, wood or other building material that is capable of bearing the superimposed weight. It may be, for example, a roof, a paved area, the ground or other underlying structure that bears the weight of the other elements.

[0071] Optional insulation/root barrier structure 2, when present, serves to prevent water from passing downward to support structure 1 and/or to prevent roots from plants growing in vegetation layer 7 from penetrating to and into support structure 1. In the illustrative embodiment shown, insulation/root barrier structure 2 includes waterproof membrane 2A and board insulation layer 2B. Waterproof membrane 2A is generally a thermoplastic rubber such as thermoplastic olefin, ethylene-propylene-diene terpolymer and polyvinylchloride. Board insulation layer 2B may be, for example, a foamed rigid polymer board such as foamed polystyrene, foamed polyurethane, foamed polyisocyanurate and the like.

[0072] Water barrier layer 3 may be, for example, a waterproof membrane as describe with respect to waterproof membrane 2A.

[0073] In the illustrative embodiment shown, drainage system 4 includes layer 4A of a geotextile, i.e., a semi-porous fabric whose function is to facilitate flow of water into one or more drainage means (not shown) through which water can be removed from the water containment system into a sewer or other system. The drainage means may include any drain or other conduit system through which water passing through drainage system 4 is removed from the water containment system. It may consists of drains, pipes, troughs or other fluid conduits, as well as associated flow management devices such as plugs, values, pumps, flow control systems and the like.

[0074] The geotextile may be, for example, an American Association of State Highway and Transportation Officials Class 1 or Class 2 geotextile. An example of a suitable geotextile is a polypropylene fabric weighing from 50 to 500 g/m.sup.2 such as is available commercially as Optigreen Separation Fabric. Layer 4A is optional and its function can be performed by the composite structure 4B. For example, composite structure 4B can be produced with one or more channels on its bottom surface, which channels form pathways through which water can flow toward the drainage means and be removed from the water containment system.

[0075] In the illustrative embodiment shown, drainage system 4 further includes porous fabric 4C and mechanical reservoir system 4D, each of which is optional and each of which can be replaced by composite structure 4B. Mechanical reservoir system 4D may be, for example, a dimpled sheet or fabric, in which water is collected in the dimples. Such a dimpled sheet is sometimes referred to as an “egg carton” structure, and may be engineered with openings through which excess water can flow to lower layers when the dimples have been filled.

[0076] Thus, drainage system 4 may consist solely of composite structure 4B, or may comprise composite structure 4B with any one or more of layers 4A, 4C and 4D, as well as other optional layers as may be desirable.

[0077] In the illustrative embodiment shown, layer 5 of water containment system 9 is a separation fabric that functions to prevent soil from washing down to lower layers while letting water pass. The separation fabric therefore is porous to water but has openings small enough to prevent soil from passing through. Separation fabric 5 may be a geotextile as described above, or other woven or non-woven fibrous material.

[0078] Layer 6 is a growth medium layer that includes organic matter and may include inorganic matter. Layer 6 preferably has moisture content at maximum holding capacity of at least 35% and a porosity at maximum water holding capacity of at least 6%, in each case as measured according to ASTM E2399.

[0079] The following examples are provided to illustrate the invention, but are not intended to limit the scope thereof. All parts and percentages are by weight unless otherwise indicated.

EXAMPLE 1 AND COMPARATIVE SAMPLES A-B

[0080] 3DL A is an ethylene-α-olefin copolymer 3-dimensional loop structure having a density of 2 pounds per cubic foot. It is made according to the general method described in WO 2016/130602.

[0081] 3DL B is an ethylene-α-olefin copolymer 3-dimensional loop structure having a density of 3 pounds per cubic foot. It is made according to the general method described in WO 2016/130602.

[0082] Foam Formulation A (FF-A) contains an isocyanate-terminated quasi-prepolymer, water and surfactants. The quasi-prepolymer contains 40% oxyethylene units and has an isocyanate content of about 7%. The water index is approximately 10,000.

[0083] Foam Formulation B (FF-B) contains an isocyanate-terminated quasi-prepolymer, water and surfactants. The quasi-prepolymer contains 63% oxyethylene units and has an isocyanate content of about 7%. The water index is approximately 10,000.

[0084] Foam Formulation C (FF-C) contains an isocyanate-terminated quasi-prepolymer, water and surfactants. The quasi-prepolymer contains 58% oxyethylene units and has an isocyanate content of about 10%. The water index is approximately 2,000.

[0085] Comparative Foams A-C and Foam Examples 1-6 are prepared by mixing the ingredients of the respective foam formulation to from a reaction mixture. The resulting reaction mixture in each case is poured into a 11.2 cm×11.2 cm×2.54 cm open mold and allowed to rise freely. For Examples 1-6, the mold contains either 3DL A or 3DL B, cut to fit the internal cavity of the mold, when the reaction mixture is poured into the mold. The 3DL material is held in place within the mold so it cannot rise with the rising foam formulation. The foam formulation rises and cures to form a foam that occupies the entire internal space of the 3DL material (when present) and fills the mold. After the foaming is complete the composite is allowed to rest for 10 minutes. The crown is removed to produce an 11.2 cm×11.2 cm×2.54 cm composite structure.

[0086] The composite structures are conditioned overnight at ambient temperature and humidity before performing property testing. Water holding, water retention and swelling are measured as described above. Results of the testing are as indicated in the following Tables 1-3.

TABLE-US-00001 TABLE 1 Composite Structures Made with Foam Formulation A Designation Comp. A* Ex. 1 Ex. 2 FF-A, parts by weight 100 67.4 60.2 3DL, type, parts by weight None A, 32.6 B, 39.8 Water holding (no applied pressure), 227 182 164 g/2.54 cm thickness Water retention, %, under applied pressures as follow: 50 lb/ft.sup.2 (2.394 kPa) 87 92 98 75 lb/ft.sup.2 (3.591 kPa) 67 80 84 112.5 lb/ft.sup.2 (5.387 kPa) 56 72 79 150 lb/ft.sup.2 (7.182 kPa) 44 62 70 Total Swelling, % 153 62 47

TABLE-US-00002 TABLE 2 Composite Structures Made with Foam Formulation B Designation Comp. B* Ex. 3 Ex. 4 FF-B, parts by weight 100 70.1 60.7 3DL, type, parts by weight None A, 29.9 B, 39.3 Water holding (no applied pressure), 192 160 156 g/2.54 cm thickness Water retention, %, under applied pressures as follow: 50 lb/ft.sup.2 (2.394 kPa) 97 96 97 75 lb/ft.sup.2 (3.591 kPa) 94 93 94 112.5 lb/ft.sup.2 (5.387 kPa) 01 90 92 150 lb/ft.sup.2 (7.182 kPa) 81 82 86 Total Swelling, % 112 56 37

TABLE-US-00003 TABLE 3 Composite Structures Made with Foam Formulation C Designation Comp. C* Ex. 5 Ex. 6 FF-C, parts by weight 100 65.6 55.1 3DL, type, parts by weight None A, 34.4 B, 44.9 Water holding (no applied pressure), 193 183 172 g/2.54 cm thickness Water retention, %, under applied pressures as follow: 50 lb/ft.sup.2 (2.394 kPa) 87 86 91 75 lb/ft.sup.2 (3.591 kPa) 57 69 77 112.5 lb/ft.sup.2 (5.387 kPa) 46 53 69 150 lb/ft.sup.2 (7.182 kPa) 36 45 56 Total Swelling, % 74 40 27

[0087] As the data in Tables 1-3 show, incorporating a 3DL structure into foams produced by any of Foam Formulations A-C has little effect on water holding. However, total swelling is reduced substantially with Examples 1-6, as compared to the corresponding comparative samples. Also, water holding under pressure is equal or improved in all instances, even when the foam formulation is adapted (as is Foam Formulation B) to have very good water holding power under pressure. The combination of initial water holding capacity, ability to hold the water under pressure and low swelling is highly beneficial and not obtained with any of the hydrophilic foams by themselves.